The present invention relates to an improved pneumatically operated debris removable grinding tool which is provided with an additional upper debris intaking wheel located on top of a fixed air guiding disc so as to effectively increase the suction force thereof whereby the grinding debris particles can be delivered to an outlet of a lower chamber and further into an air outlet duct disposed on the handle of the body even when the debris intaking wheels operate at low speed when the grinding plate abuts against the surface of a working object.
Referring to FIG. 1, a perspective diagram showing the exploded components of a prior art grinding tool disclosed in the present inventor's U.S. Pat. No. 4,930,264 is presented. This prior pneumatically operated grinding device or polishing device is equipped with an air inlet pipe 13, an air outlet pipe 14, an upper chamber 11, a lower chamber 12 on the main body 1 of the polishing device. When high pressure air is led from the air inlet pipe 13 into the upper chamber 11, the rotation shaft 211 of the pneumatic motor 21 is forced to spin with the air guiding blade assembly 22, the debris intaking wheel 23, the partition board 24 and the polishing plate 25 rotating at the same time.
As shown in FIGS. 1, 2, as the debris intaking wheel 23 rotates, an upwardly directed stirred air is produced to introduce the grinding debris into the lower chamber 12 via the through holes 251 of the polishing plate 25 and the through holes 241 of the partition board 24, and the debris particles are further led into the spacings 232 of the debris intaking wheel 23 via the through hole 231 and guided outwardly and then are cast into the center of the air guiding blade assembly 22 via the passages 221 and further led into the upper chamber 11 by way of the through hole 222. As high pressure air is discharged through the outlet port 141 of the air outlet pipe 14, a suction force will be generated as a result of vacuum state at the outlet port 141 so that debris particles can be expelled.
This prior art grinding device has some problems found in practical operation as a result of its imperfect design:
1. The debris particles led into the upper chamber 11 will be accumulated in the peripheral space between the pneumatic motor 21 and the upper chamber 11; and the suction force at the outlet port 141 is limited so that only part of the debris particles at the outlet port 141 are able to be expelled out thereof; in other words, the debris particles all around the peripheral space can not be expelled wholly and most will accumulate in the upper chamber 11 finally; and the polishing device has to be disassembled after a period of time to get the debris particles removed for further use, causing inconvenience to the operator.
2. When the grinding or polishing device is in operation, the body 1 thereof must be pressed downward with force so as to keep the polishing plate 25 in close abutment against the surface of a wood board or a wall or surface of the like to effect the polishing or grinding operation. However, the application of large force to the body 1 will cause the debris intaking wheel 23 to slow down to such an extent that the upward suction force will decline greatly, resulting in the debris particles scattered all around without being sucked therein in the practical operation.
3. The rotation shaft 211 of the pneumatic motor 21 is made in a cylindrical form so that the fixing of the air guiding blade assembly 22, the debris intaking wheel 23 to the rotation shaft 211 becomes rather difficult.